Haritima : The Environmental Society Of Hansraj College


Ozone layer

A molecule containing three atoms of oxygen is named ozone.It is very rare in our atmosphere, averaging about three molecule of ozone for every 10 million air molecules.The ozone layer is mainly found in two regions of the earth’s atmosphere.

Most ozone (about 90%) resides in a layer that begins between 6 and 10 miles (10 and 17 kms). This region of atmosphere is called Stratosphere and ozone here is commonly known as Ozone Layer.

The ozone layer is mainly found within the lower portion of stratosphere. It contains high concentrations of (O3) relative to other parts of the atmosphere.

Importance of Ozone Layer

  • O3 layer in stratosphere absorbs some of the radiation from the sun, preventing it from reaching the earth’s surface.
  • It absorbs the portion of UV light called UVB. It prevents humans, crops and marine animals from many harmful effects.
  • Basically O3 layer act as shield that absorbs 97 to 99% of the sun’s MF UV light, which otherwise would potentially damage exposed life forms near the surface.
  • It control the temperature of our earth, thus make suitable for all living organisms to survive.
  • Moreover, due to its extra heat ozonosphere also acts as a blanket that reduces the cooling rate of the earth and thus adds to the effect of water vapour.


The O3 layer present in Earth’s atmosphere reduces harmful UV radiation reaching the Earth’s surface. The lower portion of the stratosphere and has relatively high concentrations of ozone (O3).

Ozone layer depletion is- gradual thinning of the earth’s ozone layer present in the upper atmosphere. Ozone depletion also consists of a way larger springtime decrease in stratospheric ozone around Earth’s Polar Regions, which is named as the Ozone Hole.

Causes of Ozone depletion

The main reason behind ozone depletion and therefore ozone hole is Ozone Depleting Substances (ODS) and these substances have a lifetime of about 100 years.

  • Manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants, and foam- blowing agents [chlorofluorocarbons (CFCs), HCFCs, halons].

Since 1970’s, scientists observed reduction in stratospheric ozone and it had been found more prominent in Polar Regions.

    • Natural Causes:
    • The O3 layer has been found to be depleted by certain natural processes like Sun-spots and stratospheric winds. But it does not cause more than 1-2% of the ozone layer depletion.
    • The volcanic eruptions may also lead to depletion of the ozone layer.

Impacts of ozone depletion

Depletion of ozone layer affects living organisms and agriculture also.

Here are the effects of ozone depletion :-

Effects on human beings

  1. UV rays cause skin cancer.
  2. Increases the rate of non-melanin skin cancer in fair colored people.
  3. Prolonged expose to UV rays leads to Photokeratitis (slow blindness) and cataracts.

Effects on agriculture

  1. Ozone depletion affects the plants around the world, including agricultural crops.
  2. Ozone damages plants by entering leaf openings called stomata and oxidizing (burning) plant tissue during respiration. This reduces the life of plant.

Methods to regulate the O3 layer depletion

Ozone depletion can be minimised by reducing the usage of substance which release CFCs.

A project was started Montreal Protocol in 1987 under which CFCs were banned and it was estimated that ozone layer will start recovering.

We should try at our place to reduce the usage of CFCs to recover ozone layer.

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